Device for spraying and drying of paints, varnish or the like



1959 K. BRECHENMACHEI 2,868,166

DEVICE FOR SPRAYING AND DRYING OF PAINTS, VARNISH OR THE LIKE Filed' Nov. 19, 1953 INVE/W'UP Kfirealzmmaahen DEVICE FOR SPRAYING AND DRYING OF A PAINTS, VARNISH OR THE LIKE Karlmann Brechenmacher, Stuttgart, Germany Application November 19, 1953, Serial No. 393,131 Claims priority, application Germany November 24, 1952 7 Claims. (Cl. 118--643) -It is known practice when making coats of paint or other material to envelop the spray jet of atomised material of the coating with a sheathing of hot air or flames. The results obtained with these arrangements are very poor in view of the technical requirements involved as any direct contact of the atomised material with the flame sheath or the heating member has to be avoided. It is not possible to obtain with these known arrangements a homogeneous and uniform coating of paint whose quality corresponds to present day requirements. The etficiency of the drying process in these arrangements is also very low.

The use of infra-red radiation for drying coats of paint is known, this radiation acting in the layer and being greatly superior to drying by means of the heat of convection. Costly installations have hitherto been necessary for this infra-red radiation, these having to be adapted to the object to be treated. This has led to the infra-red form of drying being restricted to special cases.

The object of the present invention is to utilise the infra-red rays in a more effective manner without the use of costly installations and thus greatly enlarge the range of use of infra-red radiation. This is achieved by the invention through combining an infra-red radiator, in the form of a hand radiator, with a spray arrangement for the material to be applied, the latter having the same radiating direction. In this manner, according to the invention, in contrast to the known stationary radiation, the particles of the spray are already exposed in the spray path to the action of the radiation and the infra-red radiation acts simultaneously on the surface to be coated and on the coating itself. By combining the hitherto separate operations of first applying the coat and then treating with infra-red radiations, the invention greatly increases the output and shortens the drying operation and makes the coating adhere better. Another important advantage is that, even where curved surfaces are concerned, the irradiation can always take place at a suitable angle by guiding the radiation apparatus and the operation can be observed and regulated by controlling the spraying operation and the infra-red radiation e. g. by altering the distance from the work piece. It is thus possible to influence the preheating of the surface and the after-treatment of the coat as desired as both the spraying operation and the infra-red radiation can be used by themselves or in combined manner.

According to the invention, the infra-red radiator is combined with the spray arrangement which is for instance in the form of a spray gun in such a manner that the infra-red radiator surrounds the spray nozzle in ringmanner. Also, according to the invention, the platelike infra-red radiator surrounding the spray nozzle is provided at its rear side with heating elements and heated air is guided through flow paths to the path of the rays into the spray jet so that vapours already existing in the path to the surface to be treated are pressed out of the path of the rays. The air paths to the path of' the rays can be provided in the annular space between the infra- 2,868,166 Patented Jan. 13, 1959 red radiator and the nozzle or round its outer edge. This gives the advantage, according to the invention, that, in addition to the heat created in the spray particles by the infra-red radiation, these spray particles are also moving in a hot jet of air so that the operating conditions are further improved. The partial vacuum occ-urring at the plate-like infra-red radiator through the ejector-like acting spray jet draws in the hot air, if this latter is not supplied at a slight pressure, automatically into the jet. This serves to prevent the formation of a pressure drop at the radiation screen and also prevents the cloud of atomised material occurring during the spraying operation from reaching the radiation screen and being deposited there.

A further proposal according to the invention includes an ultra-violet radiator in the hand radiator in addition to the infra-red radiator. This allows the action of the infra-red radiation to be combined with that of the ultra-violet radiation so that complete adaptation can be made to the composition of the coating substances. This enables the invention to effect, in addition to drying through the escape of solvents, polymerisation or condensation, chemical actions through the ultra-violet radiation and particularly to acclerate the oxidation action. This enables the device to be used for coating substances of different composition.

An embodiment of the invention is illustrated in the accompanying drawing.

Figure 1 is a section through the radiation screen of a radiation arrangement.

Figure 2 is a side view of Figure l.

The arrangement a constructed in the manner of a spray gun for the coating to be sprayed on is connected by means of the hose connection b to the pressure medium pipe and is provided with the container 0 for the liquid spray material. The spray nozzle d passes through the centre of the radiator e which is shown consists of a ring-shaped concave reflector having an annular concentric depression of groove-shaped cross-section. Annular infra-red heating members 7 are fixed in the radiator. The reflecting surface of the radiator e is such that a substantially cylindrical bundle of infra-red rays is radiated out in the axial direction of the spray jet coming from the spraying nozzle d. The radiator e is provided with apertures g round the nozzle d through which air is able to pass into the radiation space and equalise the drop in pressure forming through the spray jet at the reflecting wall.

At the back of the reflector heating elements h are provided and air paths are formed by means of a parallelextending screen wall 1', these air paths being connected with the outside air by means of openings k. The reflector wall i is turned inwards at its edge so that warm air is guided from the edge to the reflecting surface of the radiator 2. This serves to prevent the formation of a partial vacuum at the radiation screen. Warm air also flows in through the apertures g located at the inner edge of its mounting. The particles of varnish or other substance in the spray jet move therefore in the hot air stream and, additionally heated, are thrown against the surface to be treated. The air which passes into the radiation space favours the drying action and it also prevents particles of paint from passing from the spray to the infra-red radiator as the effect of these particles would be to lower its action.

Pipes 1, m can also be provided on the rear side of the radiator 2, these pipes being connected up at one end to the spraying medium and compressed air supply and, at the other end, to the spraying nozzle. In this way, a heat radiation of the back wall of the radiator 2 can be utilised for pre-heating the compressed air passing to the nozzle and the spraying medium even in cases where the screen wall i and the additional heating elements h are not present.

In addition to the infra-red radiating member 1 an ultraviolet radiating. member :1 can also be provided in the reflector e.

I claim:

1. A spray gun having a spray nozzle, a ring-shaped reflector curved forward on its inner edge and mounted on said spray gun so as to surround said spray nozzle, and a ring-shaped infra-red radiator mounted in front of the reflector surface and in a plane at right angles the axis of the spray nozzle.

2. A combined spray gun and drier, comprising in combination with a spray gun having a spray nozzle: a substantially ring-shaped infra-red radiating device mounted in a plane at right angles to the axis of the spray nozzle and surrounding said spray nozzle, and a generally concave reflector mounted behind said infra-red radiating device, said reflector having a central aperture for the nozzle and being curved forward at its edge surrounding said aperture.

3. A combined spray gun and drier, comprising in combination with a spray gun having a spray nozzle: a substantially ring-shaped infra-red radiating device mount-ed in a plane at right angles to the axis of the spray nozzle and surrounding said spray nozzle, a reflector mounted behind said infra-red radiating device, said reflector having a central aperture concentric with the spray nozzle and being curved forward at its edge surrounding said aperture, and a substantially co-extensive rear wall in parallel relationship to and spaced from said reflector.

4. A combined spray gun and drier as set forth in claim 3, wherein said rear wall has its outer edge turned inwards to direct air currents passing through the space between the reflector and the rear wall towards the axis of the spray nozzle.

- combination with a spray gun having a spray nozzle:

a substantially ring-shaped infra-red radiating device mounted in a plane at right angles to the axis of the spray nozzle and surrounding said spray nozzle, a reflector mounted behind said infra-red radiating device, said reflector having a central aperture concentric with the spray nozzle and being curved forward at its edge surrounding said aperture, a rear wall substantially coextensive with said reflector and in parallel relationship to and spaced from said reflector, and electrical heating means mounted within the space between the reflector and rear wall.

6. A combined spray gun and drier as set forth in claim 5, wherein the outer edge of said rear wall extends slightly beyond the outer edge of said reflector and is bent inwardly to deflect towards the axis of the spray nozzle any air which may pass between the reflector and rear wall in a direction from the inner edge of the reflector to the outer edge of the reflector after said air has been preheated by said electrical heating means.

7. A combined spray gun and drier as set forth in claim 2, further including at least one source of ultraviolet light mounted in front of said reflector.

References Cited in the file of this patent UNITED STATES PATENTS 1,534,682 Carmean et al Apr. 21, 1925 1,824,972 Vischer Sept. 29, 1931 2,201,892 Edgar May 21, 1940 2,400,681 Bristol May 21, 1946 2,644,717 Kopperschmidt July 7, 1953 

